Count the occurrences of a value in an array

Count items strictly equal to a value.

JavaScript Version 1.0.0 · MIT · .md

function countOccurrences({ values, value }) { return values.filter(item => item === value).length; }

Input & expected output

{
  "values": [
    "delivered",
    "deferred",
    "delivered"
  ],
  "value": "delivered"
}

2

The edge case

{
  "values": [
    1,
    "1"
  ],
  "value": 1
}

1

Know the limits

• Strict equality: 1 and "1" differ.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Clone an array — Create a new array without copying the objects inside it.
• Remove duplicate values — Keep the first occurrence of each value, in its original order.
• Flatten a nested array — Turn a nested array into one sequence of values.